U.S. Pat. No. 3,239,151, the disclosure of which is incorporated herein by reference, teaches the construction of an atomiser with plunger tube, which is completely leak-proof in the normal position and contains two sealing members operatively connected to the same control element, one inserted between the plunger tube and the spray nozzle and the other on a free air passage of the container holding the liquid to be sprayed, elastic means urging those elements toward their blocking position.
In an embodiment particularly shown in FIGS. 2-3 of the aforementioned patent, this atomiser contains a pump chamber connected to the plunger tube by means of a check valve, a piston slidably mounted in that chamber, a tube slidably mounted in that piston and operatively connected to the latter so that, when the tube is moved axially, it drives the piston, a control button carrying a nozzle connecting with the tube and capable of moving the latter when the button is pressed, a valve carried on the end of the tube opposite the button and capable of being applied in proximity to said end at least one hole opening inside the piston, and a spring which is inserted between the valve and the bottom of the chamber and tends, on the one hand, to apply the valve on its seat and, on the other, to bring the piston into a rest position in which it blocks a free air opening of the container holding the liquid to be sprayed.
To use that atomiser, the tube is moved against the action of the spring by means of the button. The valve is separated from its seat, which connects the pump chamber with the nozzle; the piston is driven so that the liquid in the chamber is delivered to the nozzle to ensure spraying.
The piston initially slides with firm friction in the pump chamber. However, with time, the lip of the piston creeps due to the effect of the permanent stress applied to it; the friction between that lip and the pump chamber diminishes, resulting in a deterioration of spraying.
This addition concerns an improvement introduced in the atomiser according to the aforementioned patent, with a view to overcoming that disadvantage.